The European patent no. 0350324 describes a transition between a waveguide structure and a microstrip transmission line according to which a conducting line is supported within the waveguide perpendicular to its axis and the microstrip transmission line extends transversally through the wall of the waveguide in a position producing a coupling of energy between the microstrip transmission line and the conducting line.
The document IEEE—1995—CESLT—page 1502—“An improved approach to implement a microstrip to waveguide transition”—G. Zarba, G. Bertin, L. Accatino, P. Besso—describes a transition between a ribbed waveguide and a microstrip line arranged on a substrate. In the embodiment described, the substrate is slid under the ribbed part of the waveguide to provide it with good mechanical stability and easy assembly.
The document IEEE Proceedings of APMC 2001, Taipei, Taiwan, ROC—page 543—“A broadband Microstrip to Waveguide Transition using Planar Technique”—describes a Ka band (26-40 GHz) transition that is obtained by inserting the microwave substrate, on which a tapered microstrip line is engraved, into a rectangular waveguide partially filled with a dielectric to ensure contact-free transition with the hot conductor of the microstrip line.
The document IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, Vol. 11, No. 2, February 2001—page 68—“Integrated Microstrip and Rectangular Waveguide in Planar Form”—Dominique Deslandes and Ke Wu—Cheg-Jung Lee, Hsien-Shun Wu & Ching-Kuang C. Tzuang—presents a planar version of a Ka band transition (25-31 GHz). A guided structure is realised on a microwave substrate. The rectangular waveguide is realized by a double side metallization of the microwave substrate associated with metallized holes to realise the lateral faces of the rectangular waveguide.
These embodiments of a transition between a waveguide structure and a planar structure prove to be relatively complex to realize and require the assembly of several parts that must be all the more accurate as the operating frequencies are high. Moreover, they require microwave substrates of good quality to prevent the dielectric losses but for which the cost is high.